An electrically controlled brake system is discussed, for example, in SAE Paper 960991, using the example of an electrohydraulic brake system, in which the driver's desired braking is derived from the driver's operation of the brake pedal. This is converted into setpoint brake pressures for the individual wheel brakes, optionally taking into account other operating parameters, and optionally taking into account wheel-specific functions (for example, anti-skid systems, stability programs, etc.). These brake pressures are then regulated for each wheel by pressure control circuits on the basis of the setpoint pressure and the actual pressure measured in the area of the wheel brake.
A corresponding method or procedure based on braking torque or braking force control circuits for the individual wheels is performed in conjunction with wheel brakes having brake actuators which can be controlled by an electric motor. Braking torque or braking force control circuits can also be used in conjunction with electrohydraulic or electropneumatic brake systems.
Such electric regulators set the desired braking stipulated primarily by the driver (brake pressure, braking force, braking torque, vehicle deceleration, etc.) without regard for the respective operating situation using the dynamics of normal braking. There are operating situations in which implementation of the driver's stipulation is irrelevant for the driver. This is the case when the vehicle is standing still, for example. In this case, the driver would only like to prevent the vehicle from rolling away. If the driver's stipulation is also completely implemented in such an operating situation, vehicle comfort is limited, for example, due to adjustment noises, valve noises and pump noises. Furthermore, the vehicle electric system in this situation is unnecessarily burdened by actuation of actuators, and/or in the case of an electrohydraulic brake system, by hydraulic components and/or the controller being under load. In the case of hydraulic components, the vibration fatigue strength of the housing, and the wear on pump element gaskets, motor brushes and the valve seat are especially important.
Also, in the case of the controller, complete implementation of the driver's stipulation in such an operating situation can lead to a reduction in average component lifetime due to heating. Such an operating situation does not only occur when the vehicle is standing still, but also when the vehicle is moving in braking operations that do not require any high braking force build-up dynamics (e.g., in braking operations in which the driver does not operate the brake pedal beyond a certain extent or not at a great rate of change, or in the range of low driving speeds). Implementation of such a driver's intent (or input) with the build-up dynamics provided for sharper braking also leads to the above-mentioned loads.
Low-power measures, which prevent the controller temperature from exceeding critical levels due to self-heating, have been discussed in the context of load reduction (e.g., in German Published Patent Application No. 198 43 861).